105 lines
3.4 KiB
Python
105 lines
3.4 KiB
Python
# OSNet demux: uses the OS network stack to demultiplex incoming datagrams
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# among sockets bound to the same ports. Written by Ray Brown.
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"""OS Network UDP Demux
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This module implements a demux that uses the OS network stack to demultiplex
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datagrams coming from different peers among datagram sockets that are all bound
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to the port at which these datagrams are being received. The network stack is
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instructed as to which socket an incoming datagram should be sent to by
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connecting the destination socket to the peer endpoint.
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The OSNet demux requires operating system functionality that exists in the
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Linux kernel, but not in the Windows network stack.
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Classes:
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UDPDemux -- a network stack configuring UDP demux
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Exceptions:
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InvalidSocketError -- exception raised for improper socket objects
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KeyError -- raised for unknown peer addresses
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"""
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import socket
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from logging import getLogger
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from ..err import InvalidSocketError
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_logger = getLogger(__name__)
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class UDPDemux(object):
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"""OS network stack configuring demux
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This class implements a demux that creates sockets connected to peer
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network endpoints, configuring the network stack to demultiplex
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incoming datagrams from these endpoints among these sockets.
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Methods:
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get_connection -- create a new connection or retrieve an existing one
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service -- this method does nothing for this type of demux
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"""
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def __init__(self, datagram_socket):
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"""Constructor
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Arguments:
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datagram_socket -- the root socket; this must be a bound, unconnected
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datagram socket
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"""
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if datagram_socket.type != socket.SOCK_DGRAM:
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raise InvalidSocketError("datagram_socket is not of " +
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"type SOCK_DGRAM")
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try:
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datagram_socket.getsockname()
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except:
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raise InvalidSocketError("datagram_socket is unbound")
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try:
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datagram_socket.getpeername()
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except:
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pass
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else:
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raise InvalidSocketError("datagram_socket is connected")
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datagram_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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self._datagram_socket = datagram_socket
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def get_connection(self, address):
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"""Create or retrieve a muxed connection
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Arguments:
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address -- a peer endpoint in IPv4/v6 address format; None refers
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to the connection for unknown peers
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Return:
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a bound, connected datagram socket instance, or the root socket
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in case address was None
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"""
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if not address:
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return self._datagram_socket
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# Create a new datagram socket bound to the same interface and port as
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# the root socket, but connected to the given peer
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conn = socket.socket(self._datagram_socket.family,
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self._datagram_socket.type,
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self._datagram_socket.proto)
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conn.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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conn.bind(self._datagram_socket.getsockname())
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conn.connect(address)
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_logger.debug("Created new connection for address: %s", address)
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return conn
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@staticmethod
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def service():
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"""Service the root socket
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This type of demux performs no servicing work on the root socket,
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and instead advises the caller to proceed to listening on the root
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socket.
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"""
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return True
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